Ozone is monitored at Channel Islands NP; the other parks have nearby monitors. All network park units are in counties designated nonattainment for ozone.

The Network map below provides information on air quality monitoring. Ozone, sulfur dioxide, dry deposition, and meteorology are collected by the Clean Air Status and Trends (CASTNet) and Gaseous Pollutant Monitoring (GPMN) networks. Ozone is also monitored with passive samplers and portable continuous analyzers. Wet Deposition is monitored through cooperation with National Atmospheric Deposition Program/National Trends Network (NADP/NTN). Visibility is monitored as part of the Interagency Monitoring of Protected Visual Environments (IMPROVE). Additional details on these parameters are described in Air Quality Monitoring.

Air quality monitoring in or near the network is indicated on the map by symbols, with the blue line showing the approximate borders of the network. The legend shows the symbols for the type of monitoring present, with NPS park units in green.